阅读说明：本技术 一种电化学合成反-4-(反-4’-烷基环己基)环己基烯类液晶单体的方法 (Method for electrochemically synthesizing trans-4- (trans-4' -alkylcyclohexyl) cyclohexyl vinyl liquid crystal monomer ) 是由 韩津 刘显伟 马青松 陈芳 王晓莹 马心旺 苏建 于 2020-11-20 设计创作，主要内容包括：本发明公开了一种电化学合成反-4-(反-4’-烷基环己基)环己基烯类液晶单体的方法,包括：反-4-(反-4’-烷基环己基)环己基酮与乙烯基硅烷进行电解反应,然后在酸性催化剂下进行脱水重排异构化反应得到反-4-(反-4’-烷基环己基)环己基烯。该方法步骤短,收率高,成本低,环境友好,适合工业化生产。(The invention discloses a method for electrochemically synthesizing trans-4- (trans-4' -alkylcyclohexyl) cyclohexyl vinyl liquid crystal monomers, which comprises the following steps: the trans-4- (trans-4 '-alkylcyclohexyl) cyclohexyl ketone and vinyl silane are subjected to electrolytic reaction, and then dehydration, rearrangement and isomerization reaction is carried out under the action of an acid catalyst to obtain the trans-4- (trans-4' -alkylcyclohexyl) cyclohexyl alkene. The method has the advantages of short steps, high yield, low cost and environmental friendliness, and is suitable for industrial production.)

1. A method for electrochemically synthesizing trans-4- (trans-4' -alkylcyclohexyl) cyclohexyl vinyl liquid crystal monomers comprises the following steps:

(1) carrying out an electrolytic reaction on the compound of the formula (I) and the compound of the formula (II) to obtain a compound of a formula (III);

(2) carrying out dehydration rearrangement reaction on the compound of the formula (III) to obtain a compound of a formula (IV);

wherein the structural formulas of the compound of the formula (I), the compound of the formula (II), the compound of the formula (III) and the compound of the formula (IV) are as follows:

r1 is C_nH_2n+1N is 1,2,3,4, 5;

r2 is hydrogen or alkyl, preferably hydrogen, methyl, ethyl, propyl;

r3, R4 and R5 are the same or different and are respectively and independently selected from hydrogen, alkyl, alkoxy, phenyl and phenoxy.

2. The process according to claim 1, characterized in that the compound of formula (II) is selected from the following compounds

3. The method according to claim 1 or 2, wherein the step (1) comprises adding the compound of formula (I), the compound of formula (II), a solvent, an electrolyte, and hydrochloric acid to an electrolytic bath, and conducting an electrolytic reaction at a constant current to obtain the compound of formula (III).

4. The process according to claim 3, wherein the compound of formula (I) is used in a molar ratio of 1:1 to 2 with respect to the compound of formula (II).

5. The method according to claim 3, characterized in that the electrolyte is selected from one or a combination of tetraethylammonium chloride, tetraethylammonium bromide, tetraethylammonium benzoate, tetraethylammonium triflate, tetraethylammonium p-toluenesulfonate, tetraethylammonium trifluoroacetate, tetraethylammonium tetrafluoroborate, tetrabutylammonium chloride, tetrabutylammonium bromide, tetrabutylammonium fluoride, tetrabutylammonium iodide, tetrabutylammonium triflate, tetrabutylammonium acetate, tetrabutylammonium perchlorate and tetrabutylammonium hexafluorophosphate.

6. The method according to claim 3, wherein the solvent is selected from one or a combination of dimethyl sulfoxide, tetrahydrofuran, diethoxymethane and N, N-dimethylformamide.

7. The method according to claim 3, wherein the reaction temperature of the electrolysis reaction is preferably-20 to 10 ℃.

8. The method according to claim 1 or 2, wherein the step (2) comprises dissolving the compound of formula (III) generated in the step (1) in a solvent under the action of an acidic catalyst to obtain the compound of formula (IV).

9. The method according to claim 7, characterized in that the acidic catalyst is selected from one or a combination of sulfuric acid, hydrochloric acid, acetic acid, hydrogen fluoride, boron trifluoride, p-toluenesulfonic acid; the dosage of the acidic catalyst is 0.1-10% of the molar weight of the compound shown in the formula (III).

10. The method according to claim 7, wherein the solvent is selected from one or a combination of dichloromethane, 1, 2-dichloroethane, chloroform, fluorobenzene and toluene; the reaction temperature in the step (2) is preferably 20-50 ℃.

Technical Field

The invention relates to the field of organic synthesis, in particular to a method for electrochemically synthesizing trans-4- (trans-4' -alkylcyclohexyl) cyclohexyl vinyl liquid crystal monomers.

Background

The bicyclohexane liquid crystal has the advantages of high phase transition temperature, small viscosity, high response speed and the like, and is widely used at present. Dicyclohexylene is one of representatives of the bicyclohexane liquid crystal, and is increasingly an indispensable component in the formula of medium-high grade liquid crystal mixed materials, so that the research on a synthetic method of the bicyclohexyl ethylene is valuable.

At present, the method for synthesizing dicyclohexyl alkenes in industrial production mainly uses cyclohexyl cyclohexanone as a raw material and is obtained by steps of Wittig reaction, acidolysis reaction, isomerization under alkaline condition, Wittig reaction and the like. The method has the advantages of low molecular utilization rate, long steps, overhigh cost of Wittig reaction reagent, and large amount of triphenyl phosphine generated by Wittig reaction, and more three wastes, thus being environment-friendly.

Disclosure of Invention

Aiming at the problems in the prior art, the invention provides a method for electrochemically synthesizing trans-4- (trans-4 '-alkylcyclohexyl) cyclohexyl alkene liquid crystal monomers, the method creatively synthesizes the trans-4- (trans-4' -alkylcyclohexyl) cyclohexyl alkene compounds through an electrochemical method, and has the advantages of short steps, high yield, low cost, environmental friendliness and suitability for industrial production.

In order to achieve the purpose, the technical scheme of the invention is as follows:

a method for electrochemically synthesizing trans-4- (trans-4' -alkylcyclohexyl) cyclohexyl vinyl liquid crystal monomers comprises the following steps:

(1) carrying out an electrolytic reaction on the compound of the formula (I) and the compound of the formula (II) to obtain a compound of a formula (III);

(2) and (3) carrying out dehydration rearrangement reaction on the compound of the formula (III) to obtain the compound of the formula (IV).

The reaction formula is as follows:

wherein R is₁Is C_nH_2n+1N is 1,2,3,4, 5;

R₂hydrogen or alkyl, preferably hydrogen, methyl, ethyl, propyl;

R₃、R₄、R₅the same or different, and each is independently selected from hydrogen, alkyl, alkoxy, phenyl, and phenoxy.

Preferably, the compounds of formula (ii) according to the invention are selected from the following compounds:

the step (1) is electrochemical reaction synthesis and is carried out in an electrolytic cell, the middle of the electrolytic cell is divided into two parts by a glass diaphragm, a carbon rod is used as a cathode electrode, a platinum electrode is used as an anode electrode, and a glass electrode is used as a reference electrode.

Preferably, the step (1) is to add the compound of formula (I), the compound of formula (II), a solvent, an electrolyte and hydrochloric acid into an electrolytic bath, and perform electrolytic reaction under constant current to obtain the compound of formula (III).

The molar ratio of the compound shown in the formula (I) to the compound shown in the formula (II) is 1: 1-2.

The electrolyte is selected from one or the combination of tetraethylammonium chloride, tetraethylammonium bromide, tetraethylammonium benzoate, tetraethylammonium triflate, tetraethylammonium p-toluenesulfonate, tetraethylammonium trifluoroacetate, tetraethylammonium tetrafluoroborate, tetrabutylammonium chloride, tetrabutylammonium bromide, tetrabutylammonium fluoride, tetrabutylammonium iodide, tetrabutylammonium triflate, tetrabutylammonium acetate, tetrabutylammonium perchlorate and tetrabutylammonium hexafluorophosphate.

In the electrolytic reaction, the dosage of the electrolyte in the cathode tank is 1.5-3 times of the molar weight of the compound shown in the formula (I), and the dosage of the electrolyte in the anode tank is 1 time of the molar weight of the compound shown in the formula (I).

The solvent for the electrolysis reaction is selected fromDimethyl sulfoxide, tetrahydrofuran, diethoxymethaneAnd N, N-dimethylformamide, or a combination thereof.

In the electrolytic reaction, the concentration of the added hydrochloric acid is 10-20%, and the pH value of the system is controlled to be 3-5.

The reaction temperature of the electrolysis reaction is preferably-20-10 ℃.

In the electrolysis reaction, the electrolysis is carried out under the condition that the required electric quantity is 10-200 mA, and the reaction is stopped when the total passing electric quantity is 3-5F/mol.

Preferably, the step (2) is to dissolve the compound of formula (III) generated in the step (1) in a solvent to react under the action of an acidic catalyst to obtain the compound of formula (IV).

The acid catalyst is selected from one or the combination of sulfuric acid, hydrochloric acid, acetic acid, hydrogen fluoride, boron trifluoride and p-toluenesulfonic acid.

The dosage of the acidic catalyst is 0.1-10% of the molar weight of the compound shown in the formula (III).

The solvent is selected from one or the combination of dichloromethane, 1, 2-dichloroethane, chloroform, fluorobenzene and toluene.

The reaction temperature in the step (2) is preferably 20-50 ℃.

The term "alkyl" refers to a chain alkyl group containing 1 to 6 carbon atoms. Alkyl groups include, but are not limited to, methyl, ethyl, propyl, n-propyl, isopropyl, n-butyl, isobutyl, n-pentyl, n-hexyl, and the like.

The term "alkoxy" refers to-O- (alkyl), wherein alkyl is as defined above. Alkoxy groups include, but are not limited to, methoxy, ethoxy, propoxy, isopropoxy, butoxy, pentyloxy, hexyloxy, and the like.

Compared with the prior art, the invention has the advantages that:

(1) the invention creatively adopts an electrochemical method to synthesize the trans-4- (trans-4' -alkylcyclohexyl) cyclohexyl alkene compound, and has the advantages of high yield, low cost and environmental friendliness.

(2) The invention does not need to adopt expensive Wittig reaction reagent, greatly reduces the cost, does not generate substances such as triphenylphosphine and the like, and has simple and convenient post-treatment operation.

(3) The invention adopts two-step reaction to obtain trans-4- (trans-4' -alkylcyclohexyl) cyclohexyl alkene compounds, thereby avoiding multi-step operation; the reaction condition is milder, and the method is suitable for industrial production.

Detailed Description

The present invention is further illustrated with reference to the following specific examples, but the scope of the invention is not limited thereto.

Example 1

Placing an electrolytic tank (100mL) divided into two parts by a glass diaphragm in an ice water bath, respectively inserting a platinum sheet electrode and a carbon rod electrode into two tank chambers as an anode electrode and a cathode electrode, adding trans-4- (trans-4' -n-propylcyclohexyl) cyclohexanone (5mmol), 2-allyltrimethylsilane (8mmol), DMF (20mL), tetraethylammonium triflate (10mmol) and 10% hydrochloric acid solution into the cathode chamber, and controlling the pH of the system to be 3; tetraethylammonium triflate (5mmol), DMF (15mL) and 0.1A current are added into an anode tank, the reaction temperature is controlled to be 0 ℃, the reaction is finished after the total electrification amount reaches 3F/mol, the solution in a cathode tank is poured into 100mL of saturated saline solution, ether (50mL) is used for extraction for three times, and the solvent is removed by reduced pressure distillation, so that the organic matter (a) with the content of 95% is obtained, and the yield is 80%.

Organic substance (a) (0.5mol) and methylene chloride (300mL) were charged into a dry three-necked flask, and dissolved at 20 ℃ with stirring, and then p-toluenesulfonic acid (0.005mol) was added thereto and reacted for 20 minutes with stirring. Neutralizing with saturated sodium bicarbonate solution to pH 6.5-7, standing for layering, distilling with organic phase under reduced pressure to recover solvent to obtain solid (trans ) -4-propenyl-4' -propyl-bicyclohexane, drying, and recovering solvent with purity of 97% and yield of 99%.

¹H NMR(400MHz，CDCl₃)δ0.89(t，3H)，1.19-1.30(br，4H)，1.50(m，1H)，1.24(m，2H)，1.38-1.63(br，12H)，1.24-1.49(br，4H)，1.63(m，3H)，2.48(br，1H)，5.34(m，1H)，5.57(m，1H)。

Example 2

Placing an electrolytic cell (100mL) divided into two parts by a glass diaphragm in an ice water bath, respectively inserting a platinum sheet electrode and a carbon rod electrode serving as an anode electrode and a cathode electrode into two cell chambers, adding trans-4- (trans-4' -n-pentylcyclohexyl) cyclohexanone (5mmol), trimethoxyvinylsilane (10mmol), DMF (20mL), tetraethylammonium chloride (15mmol) and a 15% hydrochloric acid solution into the cathode chamber, and controlling the pH of the system to be 4; tetraethylammonium chloride (5mmol), DMF (15mL) and 0.2A current are added into an anode tank, the reaction temperature is controlled not to exceed 10 ℃, the reaction is finished after the total electrification amount reaches 4F/mol, the solution in a cathode tank is poured into 100mL saturated salt solution, ether (50mL) is used for extraction for three times, and the solvent is removed by reduced pressure distillation, so that the organic matter (b) with the content of 96% is obtained, and the yield is 83%.

The organic substance (b) (0.5mol) and 1, 2-dichloroethane (300mL) were added to a dry three-necked flask, and dissolved by stirring at 30 ℃ followed by addition of glacial acetic acid (0.001mol) and reaction with stirring for 20 minutes. Neutralizing the system with saturated sodium bicarbonate to pH 6.5-7, standing for layering, distilling the organic phase under reduced pressure to recover solvent, drying to obtain trans-4- (trans-4' -n-pentylcyclohexyl) cyclohexylethylene with purity of 96% and yield of 98%.

¹H NMR(400MHz，CDCl₃)δ0.88(t，3H)，1.19(m，2H)，1.28-1.29(br，6H)，1.50(m，1H)，1.24(m，2H)，1.38-1.63(br，12H)，1.24-1.49(br，4H)，2.48(br，1H)，4.94(m，1H)，4.99(m，1H)，5.79(m，1H)。

Example 3

Placing an electrolytic bath (100mL) divided into two parts by a glass diaphragm in a ice salt bath, respectively inserting a platinum sheet electrode and a carbon rod electrode into two bath chambers as an anode electrode and a cathode electrode, adding trans-4- (trans-4' -n-propylcyclohexyl) cyclohexanone (5mmol), 2- (trimethylsilyl) -1-butene (5mmol), dimethyl sulfoxide (20mL), tetrabutylammonium fluoride (15mmol) and a 20% hydrochloric acid solution into the cathode chamber, and controlling the pH of the system to be 5; tetrabutylammonium fluoride (5mmol), dimethyl sulfoxide (15mL) and 20mA current are added into an anode tank, the reaction temperature is controlled to be-10 ℃, the reaction is finished after the total electrification amount reaches 3F/mol, the solution in a cathode tank is poured into 100mL of saturated salt solution, ether (50mL) is used for extraction for three times, the solvent is removed by reduced pressure distillation, and the organic matter (c) with the content of 95% is obtained, and the yield is 82%.

Organic substance (c) (0.5mol) and toluene (300mL) were charged into a dry three-necked flask, and dissolved at 40 ℃ with stirring, and then hydrofluoric acid (0.05mol) was added and reacted with stirring for 20 minutes. Neutralizing the system with saturated sodium bicarbonate solution to pH 6.5-7, standing for layering, distilling under reduced pressure to recover solvent to obtain solid (trans ) -4-butenyl-4' -propyl-bicyclohexane, drying, and recovering solvent with purity of 97% and yield of 99%.

¹H NMR(400MHz，CDCl₃)δ0.79(t，3H)，0.89(t，3H)，1.19-1.30(br，4H)，1.50(m，1H)，1.24(m，2H)，1.38-1.63(br，12H)，1.24-1.49(br，4H)，2.00(m，2H)，2.48(br，1H)，5.35(m，1H)，5.57(m，1H)。

Example 4

Placing an electrolytic tank (100mL) divided into two parts by a glass diaphragm in an ice water bath, respectively taking a platinum sheet electrode and a carbon rod electrode as an anode electrode and a cathode electrode to be inserted into two tank chambers, adding trans-4- (trans-4' -n-pentylcyclohexyl) cyclohexanone (5mmol), 2-allyltrimethylsilane (10mmol), dimethyl sulfoxide (20mL), tetrabutylammonium iodide (10mmol) and a 10% hydrochloric acid solution into the cathode chamber, and controlling the pH of the system to be 5; tetrabutylammonium iodide (5mmol), dimethyl sulfoxide (15mL) and 10mA current are added into an anode tank, the reaction temperature is controlled to be 0 ℃, the reaction is finished after the total electrification amount reaches 3F/mol, the solution in a cathode tank is poured into 100mL of saturated salt solution, extraction is carried out for three times by using ether (50mL), and the solvent is removed by reduced pressure distillation, so that the organic matter (d) with the content of 97 percent and the yield of 86 percent is obtained.

Organic substance (d) (0.5mol) and fluorobenzene (300mL) were charged into a dry three-necked flask, and dissolved by stirring at 35 ℃ followed by addition of sulfuric acid (0.0005mol) and reaction with stirring for 20 minutes. Neutralizing the system with saturated sodium bicarbonate solution to pH 6.5-7, standing for layering, distilling with organic phase under reduced pressure to recover solvent to obtain solid (trans ) -4-propenyl-4' -n-pentyl-bicyclohexane, drying, and obtaining purity of 98% and yield of 99%.

¹H NMR(400MHz，CDCl₃)δ0.88(t，3H)，1.19(m，2H)，1.28-1.29(br，6H)，1.50(m，1H)，1.24(m，2H)，1.38-1.63(br，12H)，1.24-1.49(br，4H)，1.63(m，3H)，2.48(br，1H)，5.34(m，1H)，5.57(m，1H)。

Example 5

Placing an electrolytic bath (100mL) divided into two parts by a glass diaphragm in a ice salt bath, respectively inserting a platinum sheet electrode and a carbon rod electrode into two bath chambers as an anode electrode and a cathode electrode, adding trans-4- (trans-4' -methylcyclohexyl) cyclohexanone (5mmol), 2- (dimethylphenylsilyl) -1-pentene (10mmol), tetrahydrofuran (20mL), tetraethylammonium tetrafluoroborate (10mmol) and a 15% hydrochloric acid solution into the cathode chamber, and controlling the pH of the system to be 4; tetraethylammonium tetrafluoroborate (5mmol), tetrahydrofuran (15mL) and 50mA current are added into an anode tank, the reaction temperature is controlled to be-20 ℃, the reaction is finished after the total electrification amount reaches 4F/mol, the solution in a cathode tank is poured into 100mL of saturated saline solution, ether (50mL) is used for extraction for three times, and the solvent is removed by reduced pressure distillation, so that the organic matter (e) with the content of 97 percent and the yield of 85 percent is obtained.

The organic substance (e) (0.5mol) and methylene chloride (300mL) were charged into a dry three-necked flask, and dissolved at 50 ℃ with stirring, and then hydrochloric acid (0.001mol) was added to the mixture to react for 20 minutes with stirring. Neutralizing the system with saturated sodium bicarbonate solution to pH 6.5-7, standing for layering, distilling with organic phase under reduced pressure to recover solvent to obtain solid (trans ) -4-pentenyl-4' -methyl-bicyclohexane, drying, and obtaining product with purity of 98% and yield of 99%.

¹H NMR(400MHz，CDCl₃)δ0.86(d，3H)，0.96(t，3H)，1.24(m，2H)，1.46(m，2H)，1.54(m，1H)，1.38-1.63(br，12H)，1.24-1.49(br，4H)，1.98(m，2H)，2.48(br，1H)，5.35(m，1H)，5.57(m，1H)。

Example 6

Placing an electrolytic bath (100mL) divided into two parts by a glass diaphragm in a ice salt bath, respectively inserting a platinum sheet electrode and a carbon rod electrode into two bath chambers as an anode electrode and a cathode electrode, adding trans-4- (trans-4' -ethylcyclohexyl) cyclohexanone (5mmol), triisopropoxyethylene silane (10mmol), DMF (20mL), tetrabutylammonium tetrafluoroborate (10mmol) and a 15% hydrochloric acid solution into the cathode chamber, and controlling the pH of the system to be 3; tetrabutylammonium tetrafluoroborate (5mmol), DMF (15mL) and 20mA current are added into an anode tank, the reaction temperature is controlled to be-10 ℃, the reaction is finished after the total electrification amount reaches 4F/mol, the solution in a cathode tank is poured into 100mL of saturated salt solution, ether (50mL) is used for extraction for three times, the solvent is removed by reduced pressure distillation, and the organic matter (e) is obtained, wherein the content is 97%, and the yield is 80%.

Organic substance (f) (0.5mol) and methylene chloride (300mL) were charged into a dry three-necked flask, and dissolved by stirring at 50 ℃ followed by addition of a glacial acetic acid-boron trifluoride (1:1) mixture (0.001mol) and reaction with stirring for 20 minutes. Neutralizing the system with saturated sodium bicarbonate solution to pH 6.5-7, standing for layering, vacuum distilling to recover solvent to obtain solid trans-4- (trans-4' -ethylcyclohexyl) cyclohexylethylene with purity 97% and yield 97%.

1H NMR(400MHz，CDCl3)δ0.99(t，3H)，1.20(m，2H)，1.24(m，2H)，1.50(m，1H)，1.38-1.63(br，12H)，1.24-1.49(br，4H)，2.48(br，1H)，4.94(m，1H)，4.99(m，1H)，5.79(m，1H)。

Example 7

Placing an electrolytic bath (100mL) divided into two parts by a glass diaphragm in a ice salt bath, respectively taking a platinum sheet electrode and a carbon rod electrode as an anode electrode and a cathode electrode to be inserted into two bath chambers, adding trans-4- (trans-4' -n-butylcyclohexyl) cyclohexanone (5mmol), triphenylvinylsilane (10mmol), DMF (20mL), tetrabutylammonium chloride (10mmol) and a 15% hydrochloric acid solution into the cathode bath, and controlling the pH of the system to be 4; tetrabutylammonium chloride (5mmol), DMF (15mL) and 50mA current are added into an anode tank, the reaction temperature is controlled to be-20 ℃, the reaction is finished after the total electrification amount reaches 4F/mol, the solution in a cathode tank is poured into 100mL saturated salt solution, ether (50mL) is used for extraction for three times, and the solvent is removed by reduced pressure distillation, so that the organic matter (e) with the content of 97 percent and the yield of 81 percent is obtained.

Organic material (g) (0.5mol) and toluene (300mL) were charged into a dry three-necked flask, and dissolved at 50 ℃ with stirring, and then p-toluenesulfonic acid (0.001mol) was added to the mixture to react with stirring for 20 minutes. Neutralizing the system with saturated sodium bicarbonate solution to pH 6.5-7, standing for layering, distilling the organic phase under reduced pressure to recover solvent to obtain solid trans-4- (trans-4' -n-butylcyclohexyl) cyclohexylethylene with purity of 97% and yield of 98%.

1H NMR(400MHz，CDCl3)δ0.88(t，3H)，1.19-1.29(m，6H)，1.24(m，2H)，1.50(m，1H)，1.38-1.63(br，12H)，1.24-1.49(br，4H)，2.48(br，1H)，4.94(m，1H)，4.99(m，1H)，5.79(m，1H)。

The foregoing description of specific embodiments of the present invention has been presented. It is to be understood that the invention is not limited to the embodiments described above, which are described in the specification only to illustrate the principles of the invention. The invention also includes various insubstantial changes and modifications within the spirit of the invention, as claimed by those skilled in the art.